Deuterium Nuclei Research Articles

The NH2D hyperfine structure revealed by astrophysical observations

The 1$_{11}$-1$_{01}$ lines of ortho and para--NH$_2$D (o/p-NH$_2$D), respectively at 86 and 110 GHz, are commonly observed to provide constraints on the deuterium fractionation in the interstellar medium. In cold regions, the hyperfine structure due to the nitrogen ($^{14}$N) nucleus is resolved. To date, this splitting is the only one which is taken into account in the NH$_2$D column density estimates. We investigate how the inclusion of the hyperfine splitting caused by the deuterium (D) nucleus affects the analysis of the rotational lines of NH$_2$D. We present 30m IRAM observations of the above mentioned lines, as well as APEX o/p-NH$_2$D observations of the 1$_{01}$-0$_{00}$ lines at 333 GHz. The hyperfine spectra are first analyzed with a line list that only includes the hyperfine splitting due to the $^{14}$N nucleus. We find inconsistencies between the line widths of the 1$_{01}$-0$_{00}$ and 1$_{11}$-1$_{01}$ lines, the latter being larger by a factor of $\sim$1.6$\pm0.3$. Such a large difference is unexpected given the two sets of lines are likely to originate from the same region. We next employ a newly computed line list for the o/p-NH$_2$D transitions, where the hyperfine structure induced by both nitrogen and deuterium nuclei is included. With this new line list, the analysis of the previous spectra leads to linewidths which are compatible. Neglecting the hyperfine structure owing to D leads to overestimate the linewidths of the o/p-NH$_2$D lines at 3 mm. The error for a cold molecular core is about 50\%. This error propagates directly to the column density estimate. It is therefore recommended to take into account the hyperfine splittings caused by both the $^{14}$N and D nuclei in any analysis relying on these lines.

Electron spin echo envelope modulation of molecular motions of deuterium nuclei

Electron Spin Echo Envelope Modulation (ESEEM) spectroscopy is a powerful technique for the study of hyperfine interactions between an unpaired electron and nearby nuclei in solids, and is employed in quantitative structural studies. Here, we describe the use of ESEEM to study the slow motion of deuterium nuclei using their nuclear quadrupole resonance (NQR) line shapes. Two ESEEM techniques were employed: the conventional three-pulse ESEEM experiment, π/2 – τ – π/2 – T– π/2 – τ – echo, and the four-pulse ESEEM, π/2 – τ – π/2 – T/2 – π – T/2 – π/2 – τ – echo, with the time variable T scanned in both cases. The nitroxide free radical 4-tert-butyliminomethyl-2,2,5,5-tetramethyl(d12)-3-imidazoline-1-oxyl with four deuterated methyl groups was investigated in a glassy ortho-terphenyl matrix over a wide temperature range. It was shown that four-pulse ESEEM allowed measurement of the nearly pure 2H NQR line shape. Between 90K and 120K, the ESEEM spectra change drastically. At low temperatures, four-pulse ESEEM spectra show a Pake-like pattern, which evolves into a single line at higher temperatures, which is typical for NQR of rotating methyl CD3 groups. Comparison with literature data on NQR allows estimation of the reorientation rate, k. At ∼100K, where the spectral changes are most pronounced, k was found to be ∼105s−1. The spectral linewidths for the three-pulse ESEEM were found to decrease similarly with increasing temperature; so the three-pulse technique is also capable to detect motion of this type. The ESEEM approach, along with site-directed spin labeling, may be useful for detection of motional transitions near the spin labels in biological systems, when information on motion is required in a wide temperature range.

Pulse height model for deuterated scintillation detectors

An analytical model of light pulse height distribution for finite deuterated scintillation detectors is created using the impulse approximation. Particularly, the energy distribution of a scattered neutron is calculated based on an existing collision probability scheme for general cylindrical shaped detectors considering double differential cross-sections. The light pulse height distribution is analytically and numerically calculated by convoluting collision sequences with the light output function for an EJ-315 detector from our measurements completed at Ohio University. The model provides a good description of collision histories capturing transferred neutron energy in deuterium-based scintillation materials. The resulting light pulse height distribution details pulse compositions and their corresponding contributions. It shows that probabilities of neutron collision with carbon and deuterium nuclei are comparable, however the light pulse amplitude due to collisions with carbon nuclei is small and mainly located at the lower region of the light pulse distribution axis. The model can explore those neutron interaction events that generate pulses near or below a threshold that would be imposed in measurements. A comparison is made between the light pulse height distributions given by the analytical model and measurements. It reveals a significant probability of a neutron generating a small light pulse due to collisions with carbon nuclei when compared to larger light pulse generated by collisions involving deuterium nuclei. This model is beneficial to understand responses of scintillation materials and pulse compositions, as well as nuclei information extraction from recorded pulses.

THE HYPERFINE STRUCTURE OF THE ROTATIONAL SPECTRUM OF HDO AND ITS EXTENSION TO THE THz REGION: ACCURATE REST FREQUENCIES AND SPECTROSCOPIC PARAMETERS FOR ASTROPHYSICAL OBSERVATIONS

The rotational spectrum of the mono-deuterated isotopologue of water, HD16O, has been investigated in the millimeter- and submillimeter-wave frequency regions, up to 1.6 THz. The Lamb-dip technique has been exploited to obtain sub-Doppler resolution and to resolve the hyperfine (hf) structure due to the deuterium and hydrogen nuclei, thus enabling the accurate determination of the corresponding hf parameters. Their experimental determination has been supported by high-level quantum-chemical calculations. The Lamb-dip measurements have been supplemented by Doppler-limited measurements (weak high-J and high-frequency transitions) in order to extend the predictive capability of the available spectroscopic constants. The possibility of resolving hf splittings in astronomical spectra has been discussed.

Nuclear fusion: bringing a star down to Earth

Nuclear fusion offers the potential for being a near limitless energy source by fusing together deuterium and tritium nuclei to form helium inside a plasma burning at 100 million K. However, scientific and engineering challenges remain. This paper describes how such a plasma can be confined on Earth, and discusses the similarities and differences with fusion in stars. It focuses on the magnetic confinement technique and, in particular, the method used in a tokamak. The confinement achieved in the equilibrium state is reviewed and it is shown how the confinement can be too good, leading to explosive instabilities at the plasma edge called edge localised modes (ELMs). It is shown how the impact of ELMs can be minimised by the application of magnetic perturbations and discusses the physics behind the penetration of these perturbations into what is ideally a perfect conducting plasma.

Cold nuclear fusion

If target deuterium atoms were implanted in a metal crystal in accelerator experiments, a sharp increase in the probability of DD-fusion reaction was clearly observed when compared with the reaction’s theoretical value. The electronic screening potential, which for a collision of free deuterium atoms is about 27eV, reached 300–700eV in the case of the DD-fusion in metallic crystals. These data leads to the conclusion that a ban must exist for deuterium atoms to be in the ground state 1s in a niche filled with free conduction electrons. At the same time, the state 2p whose energy level is only 10eV above that of state 1s is allowed in these conditions. With anisotropy of 2p, 3p or above orbitals, their spatial positions are strictly determined in the lattice coordinate system. When filling out the same potential niches with two deuterium atoms in the states 2p, 3p or higher, the nuclei of these atoms can be permanently positioned without creating much Coulomb repulsion at a very short distance from each other. In this case, the transparency of the potential barrier increases dramatically compared to the ground state 1s for these atoms. The probability of the deuterium nuclei penetrating the Coulomb barrier by zero quantum vibration of the DD-system also increases dramatically. The so-called cold nuclear DD-fusion for a number of years was registered in many experiments, however, was still rejected by mainstream science for allegedly having no consistent scientific explanation. Finally, it received the validation. Below, we outline the concept of this explanation and give the necessary calculations. This paper also considers the further destiny of the formed intermediate state of 4He∗.

Variations in GC–MS Response Between Analytes and Deuterated Analogs

Isotopic analogs are commonly used as appropriate internal standards. It was observed that analytes usually have higher mass responses than their equimolar deuterated analogs leading to quantification discrepancy. The standard addition method was adopted on dimethyl azelate (DMA) and d 6-dimethyl azelate (d 6-DMA) to investigate possible reasons for this behavior. Cross contribution of mass responses, intermolecular deuterium–hydrogen exchange during chromatographic separation, and deviation in mass ionization response of C–H against C–D bonds were studied. GC–MS analysis revealed that neither cross contribution of ions nor H2/H exchange was responsible for the difference in responses between DMA and d 6-DMA. On the other hand, a study of carbon nucleus relaxation conducted by 13C-NMR showed that relaxation rate of carbonyl carbon in d 6-DMA is faster than DMA (9 and 3 s−1, respectively). This indicates rapid interaction between spin of deuterium nucleus with spin of unpaired electrons in the structure. Accordingly, DMA has more electrons in triplet/singlet state (i.e., unpaired electrons) in each time moment promoting propagation of radicalization reactions inside the electron impact chamber. In conclusion, this should increase the response of total ion current (TIC) and generate overestimated results for equimolar ratios of analytes such as dimethyl azelate, dimethyl adipate and dimethyl phthalate against their deuterated counterparts.

Quantum algorithms for computational nuclear physics

While quantum algorithms have been studied as an efficient tool for the stationary state energy determination in the case of molecular quantum systems, no similar study for analogical problems in computational nuclear physics (computation of energy levels of nuclei from empirical nucleon-nucleon or quark-quark potentials) have been realized yet. Although the difference between the above mentioned studies might seem negligible, it will be examined. First steps towards a particular simulation (on classical computer) of the Iterative Phase Estimation Algorithm for deuterium and tritium nuclei energy level computation will be carried out with the aim to prove algorithm feasibility (and extensibility to heavier nuclei) for its possible practical realization on a real quantum computer.

The Structure and Function of Supramolecular Self-Assembling Binary Guanosine Gels

Binary liquid crystals of guanosine (GUO) and guanosine-5′-monophosphate (GMP) have been found to have unique and interesting properties in their ability to solubilize and selectively purify nanoparticles. The thermoassociative properties of these GMP-GUO g-gel phases have not been thoroughly explored and the mechanism of action is not understood. In the present study, nuclear magnetic resonance spectroscopy is used to probe the anisotropic properties of binary liquid crystals by employing deuterium nuclei. Deuterons have a quadrupolar moment that is normally averaged out by rapid molecular reorientation. In liquid crystals, however, the motion of the molecules is constrained such that quadrupolar effects are displayed in spectral data. To prevent other effects such as bulk exchange of deuterons from impacting the signal, 2H5-labeled aniline is employed to study the supramolecular structure of the liquid crystalline gels. This isotopomer of aniline has deuterons that are strongly bound to a rigid aromatic ring, allowing for study of solvent directed interactions without concern for conformation or bulk exchange effects. This study determines the anisotropy and order parameter of the binary liquid crystals to elucidate the structural and functional properties of the system.∗This research is supported by the Photosynthetic Systems Program, Office of Basic Energy Sciences, United States Department of Energy (DE-FG02-07ER15903).

Determining the parity of a permutation using an experimental NMR qutrit

We present the NMR implementation of a recently proposed quantum algorithm to find the parity of a permutation. In the usual qubit model of quantum computation, speedup requires the presence of entanglement and thus cannot be achieved by a single qubit. On the other hand, a qutrit is qualitatively more quantum than a qubit because of the existence of quantum contextuality and a single qutrit can be used for computing. We use the deuterium nucleus oriented in a liquid crystal as the experimental qutrit. This is the first experimental exploitation of a single qutrit to carry out a computational task.

High resolution 2H NMR spectroscopy at the natural abundance level of deuterium

The relaxation time, T1, of deuterium nuclei in a few deuterated compounds, such as methanol-d4, benzene-d6, and dimethylsulfoxide-d6, is measured at higher temperatures in the range from 300 to 375 K. An almost linear increase in time, T1, over an increase in temperature is observed in all these cases, which confirms an increase in the mobility of molecules and a decrease in the correlation time. A T1 value in the range from 2 to 3 s can be expected for deutrons in small organic molecules at temperatures above 350 K. Thus, a linewidth of about 0.1 Hz in 2H NMR spectra can be obtained for a magnetic field inhomogeneity of about 0.5 Hz in 1H NMR spectra. Such high resolution 2H NMR spectra provide information about chemical shifts and J(H-D) spin-spin coupling constants (or J(H-H) = (γH/γD)J(H-D) when the isotope effects on the spin-spin coupling constants are neglected), including information about coupling constants between magnetically equivalent protons that can not be observed in 1H NMR spectra. New or refined data on the coupling constants are obtained from the studied 2H NMR spectra for ethanol, propanol, 1,2-dichloroethane, and 1,4-dioxane.

Fusion 2050 – European and Polish Perspective

Abstract Fusion, in all its varieties, is a very current subject of science and technology. The results of strongly exothermic reaction of thermonuclear fusion between nuclei of deuterium and tritium are: helium nuclei and neutrons, plus considerable kinetic energy of neutrons of over 14 MeV. DT nuclides synthesis reaction is probably not the most favorable one for energy production, but is the most advanced technologically. More efficient would be possibly an aneutronic fusion. The EU by its EURATOM agenda prepared a Road Map for research and implementation of Fusion as a commercial method of thermonuclear energy generation in the time horizon of 2050.The milestones on this road are tokomak experiments JET, ITER and DEMO, and neutron experiment IFMIF. There is a hope, that by engagement of the national government, and all research and technical fusion and plasma communities, part of this Road Map may be realized in Poland. The infrastructure build for fusion experiments may be also used for material engineering research, chemistry, biomedical, associated with environment protection, power engineering, security, etc. Construction of such research and industrial accelerator and tokomak infrastructure may have potentially a profound meaning for the development of science and technology in Poland.

Impact of hadronic and nuclear corrections on global analysis of spin-dependent parton distributions

We present the first results of a new global next-to-leading order analysis of spin-dependent parton distribution functions from the most recent world data on inclusive polarized deep-inelastic scattering, focusing in particular on the large-x and low-Q^2 regions. By directly fitting polarization asymmetries we eliminate biases introduced by using polarized structure function data extracted under nonuniform assumptions for the unpolarized structure functions. For analysis of the large-x data we implement nuclear smearing corrections for deuterium and 3He nuclei, and systematically include target mass and higher twist corrections to the g_1 and g_2 structure functions at low Q^2. We also explore the effects of Q^2 and W^2 cuts in the data sets, and the potential impact of future data on the behavior of the spin-dependent parton distributions at intermediate and large x.

Ultrafast 1H J-resolved spectroscopy via 2H distant dipolar field in magnetic fields with unknown spatial variations

Spatially encoded ultrafast NMR accelerates the acquisition of 2D NMR spectra by orders of magnitude, but it is affected by field inhomogeneity. To circumvent this influence, various approaches have been proposed. Here we propose a new scheme to ultrafast achieve 2D J-resolved spectroscopy in inhomogeneous fields via the distant dipolar field of deuterium nuclei. Compared to the methods via homonuclear distant dipolar field, the trouble of selective excitation and solvent suppression when the peaks of solvent and solute spins are close to each other in inhomogeneous fields will be avoided. Theoretical analyses and experimental results are presented for verification.

Glycerol penetration profile in phospholipid bilayers measured by ESEEM of spin-labelled lipids

Electron spin echo envelope modulation (ESEEM) spectroscopy of phospholipids systematically spin-labelled along the sn-2 chain was used to detect the penetration of a deuterium-substituted water–glycerol mixture H2O/C3D5(OH)3 (1:1 v/v) into dipalmitoyl phosphatidylcholine (DPPC) bilayer membranes. The results provide a detailed profile of the penetration of glycerol across the membrane. The ESEEM amplitude induced by the hyperfine interaction with the deuterium nuclei drops substantially beyond the 10th label position. Beyond the 12th label position, the amplitude was nearly constant. A quantitative assessment of the glycerol concentration in the middle of the bilayer resulted in a value of ∼0.4 M (∼3% v/v). For comparison, analogous measurements were performed for the penetration of pure deuterium water D2O. In both cases, the ESEEM amplitudes varied similarly across the bilayer, except for the terminal 16th position. At this position, the amplitude for pure water was small and close in magnitude to the noise level.

Synthesis of new structures in dense deuterium gas and deuterated palladium under nuclear reactions induced by γ quanta

Effects of the change in chemical composition of initially pure Pd (99.997%) and formation of a new product after γ irradiation (8.8 MeV) of a Pd target in a gaseous deuterium environment are ascertained experimentally. A phenomenological model is presented to explain the observed effects by means of the chain reactions of fusion of light nuclei and Pd nuclear fission into lighter products due to photodisintegration of deuterons on neutrons and protons, and nuclear reactions with heating and fusion of deuterium nuclei. Similar reactions in dense deuterium gas or deuterated metals could serve as the basis for the creation of a fundamentally new deuterated fission/fusion reactor.

Phenomenological nuclear-reaction description in deuterium-saturated palladium and synthesized structure in dense deuterium gas under γ-quanta irradiation

The observed phenomena of changes of chemical compositions in previous reports [1, 2] allowed us to develop a phenomenological nuclear fusion-fission model with taking into consideration the elastic and inelastic scattering of photoprotons and photoneutrons, heating of surrounding deuterium nuclei, following d-d fusion reactions and fission of middle-mass nuclei by “hot” protons, deuterons and various-energy neutrons. Such chain processes could produce the necessary number of neutrons, “hot” deuterons for explanation of observed experimental results [1, 2]. The developed approach can be a basis for creation of deuterated nuclear fission reactors (DNFR) with high-density deuterium gas and the so-called deuterated metals. Also, this approach can be used for the study of nuclear reactions in high-density deuterium or tritium gas and deuterated metals.

1932, a watershed year in nuclear physics

The consequences, for good and ill, of that annus mirabilis of discovery and invention are still very much with us.

Gas samples with a mixture of hydrogen isotopes and 3He for NMR spectroscopy and estimation of the magnetic moment of the 3He nucleus

We describe the technique for preparing high-pressure glass ampoules for NMR spectroscopy, which contain hydrogen isotopes (deuterium and protium) as well as the light helium isotope (3He). Using these ampoules, we succeeded in measuring the spin precession frequencies for 3He nuclei and the molecular deuterium nuclei and in calculating one of the fundamental physical constants, viz., the ratio of the magnetic moments of the helion and the proton μh/μp = −0.761 812 215(3).

Enhancement of Electron Spin Echo Envelope Modulation Spectroscopic Methods to Investigate the Secondary Structure of Membrane Proteins

This paper reports on a significant improvement of a new structural biology approach designed to probe the secondary structure of membrane proteins using the pulsed EPR technique of electron spin echo envelope modulation (ESEEM) spectroscopy. Previously, we showed that we could characterize an α-helical secondary structure with ESEEM spectroscopy using a (2)H-labeled Val side chain coupled with site-directed spin-labeling (SDSL). In order to further develop this new approach, molecular dynamic (MD) simulations were conducted on several different hydrophobic residues that are commonly found in membrane proteins. (2)H-SL distance distributions from the MD results indicated that (2)H-labeled Leu was a very strong candidate to significantly improve this ESEEM approach. In order to test this hypothesis, the secondary structure of the α-helical M2δ peptide of the acetylcholine receptor (AChR) incorporated into a bicelle was investigated with (2)H-labeled Leu d(10) at position 10 (i) and nitroxide spin labels positioned 1, 2, 3, and 4 residues away (denoted i+1 to i+4) with ESEEM spectroscopy. The ESEEM data reveal a unique pattern that is characteristic of an α-helix (3.6 residues per turn). Strong (2)H modulation was detected for the i+3 and i+4 samples, but not for the i+2 sample. The (2)H modulation depth observed for (2)H-labeled d(10) Leu was significantly enhanced (×4) when compared to previous ESEEM measurements that used (2)H-labeled d(8) Val. Computational studies indicate that deuterium nuclei on the Leu side chain are closer to the spin label when compared to Val. The enhancement of (2)H modulation and the corresponding Fourier Transform (FT) peak intensity for (2)H-labeled Leu significantly reduces the ESEEM data acquisition time for Leu when compared to Val. This research demonstrates that a different (2)H-labeled amino acid residue can be used as an efficient ESEEM probe further substantiating this important biophysical technique. Finally, this new method can provide pertinent qualitative structural information on membrane proteins in a short time (few minutes) at low sample concentrations (~50 μM).